chore: add husky pre-commit hook and lint-staged configuration

- Created a pre-commit hook in .husky to run lint-staged.
- Added .lintstagedrc.mjs to format frontend files with Prettier and apply Spotless to backend Java files.
- Introduced .prettierignore to exclude specific directories from formatting.

.prettierignore

@@ -0,0 +1,5 @@
+.agents/
+.husky/
+backend/target/
+backend/src/main/resources/templates/
+frontend/node_modules/